As rotation transmission devices configured to selectively perform and stop the transmission of the rotation of an input shaft to an output shaft, rotation transmission devices are known which include a two-way clutch configured to connect the input and output shafts to each other and disconnect the input and output shafts from each other, and an electromagnetic clutch configured to selectively engage and disengage the two-way clutch.
Japanese Unexamined Patent Application Publication No. 2013-199993 discloses a rotation transmission device including an outer ring, an inner ring provided inside of the outer ring, a control retainer and a rotary retainer which are provided between the outer ring and the inner ring such that pillars of the control retainer circumferentially alternate with pillars of the rotary retainer, opposed pairs of rollers received in pockets defined between adjacent ones of the pillars of the control retainer and the pillars of the rotary retainer, and elastic members received between the respective opposed pairs of rollers. Each opposed pair of rollers are biased away from each other by the elastic member so as to be kept at the standby position at which the pair of rollers engage with a cylindrical surface formed on the inner periphery of the outer ring and one of cam surfaces formed on the outer periphery of the inner ring, and when the inner ring rotates in one direction, one of each opposed pair of rollers engages with the cylindrical surface and one of the cam surfaces, thereby transmitting the rotation of the inner ring to the outer ring.
The rotation transmission device of Japanese Unexamined Patent Application Publication No. 2013-199993 further includes an input shaft to which the inner ring is mounted, and an electromagnetic clutch having an electromagnetic coil, and being provided on the input shaft. When the electromagnetic coil of the electromagnetic clutch is energized and thus the control retainer axially moves, due to a torque cam (motion converting mechanism) provided between the opposed surfaces of a flange of the control retainer and a flange of the rotary retainer, the control retainer and the rotary retainer rotate relative to each other in the direction in which the circumferential widths of the respective pockets decrease, so that the pairs of rollers are moved to their disengaged position by the pillars of the control retainer and the respective pillars of the rotary retainer, thereby stopping the transmission of the rotation of the inner ring to the outer ring.
In the above rotation transmission device, when the electromagnetic coil of the electromagnetic clutch is de-energized, due to the pressing force of the elastic members received between the respective opposed pairs of rollers, the control retainer and the rotary retainer rotate relative to each other in the direction in which the circumferential widths of the respective pockets increase, so that the pairs of rollers instantly engage with the cylindrical surface and the respective cam surfaces. Therefore, the rollers scarcely move in the rotational direction, and can respond quickly.